Síntese da estrutura metalorgânica ZIF-zni para aplicação no tratamento de efluentes oleosos

Abstract

Improper disposal of waste oily waters drastically impacts the environment. Oils and greases are the focus of studies and research to minimize the actions resulting from this disposal when performed in the environment without any type of previous treatment. Oil/water emulsions are highly stable mixtures of oil in water and presenting stability, they remain longer in the environment, preventing the passage of sunlight to aquatic environments by decreasing the oxygen level of the waters. Metalorganic structures are configured as hybrid compounds that present high potential in oil adsorption. Within this context, this work aimed to synthesize the Zeolitic Imidazolate Framework of dense phase ZIF-zni and propose a synthesis mechanism. In addition, evaluate the potential of ZIF-zni as adsorbent in the oil/water emulsion separation process. ZIF-zni, polymorphized to ZIF-4, was prepared using solvetopmic method, at a temperature of 25 °C for 1 hour, with synthesis time of 30 minutes. The synthesis product was washed with Methyl Alcohol and dried at 60 °C for 24 hours. ZIF-zni was characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Infrared Spectroscopy (IR), Thermogravimetry (TG) and Contact Angle (CA). 19 experiments were carried out in finite bathing system, based on a factorial planning 2³ with triplicate at the central point and duplicate in the other points. The variables under study were the initial concentration of the oil/water emulsion (100, 200 and 300 mg. L-1), the contact time between the adsorbent and the emulsion (2, 4 and 6 hours) and temperature (30, 45 and 60 ºC). Through a calibration curve previously performed and the use of a spectrophotometer, it was possible to analyze the concentrations of emulsions and the tests performed. From these results, the %Rem removal percentage and the qeq removal capacity in relation to the oil/water emulsion were calculated. The Zeolitic Imidazolate Framework was successfully obtained, presenting well-defined peaks, configuring the material as crystalline. Through Scanning Electron Microscopy, it was noticed that the ZIF-zni obtained presents heterogeneous rod-shaped morphology. The thermogravimetric analysis allowed the verification of the thermal stability of the ZIF zni of 500 ºC. Through the Contact Angle Test it was possible to identify that the ZIF zni is configured as a hydrophilic material, with a contact angle equal to 82.51 º. Through the Analysis of variance, it was possible to detect the main factors that influence the results of removal percentage and adsorption capacity, elaborating models that correspond to the results obtained in 98.90 % and 99.96% respectively. A synthesis mechanism for ZIF-zni has been proposed. This research has relevance in the academic scope by presenting the first application of ZIF-zni as adsorbent in the process of separation oil/water emulsion.